Fabrication of semiconductors typically comprises many steps, including creation of a silicon wafer, deposition of various materials onto the wafer, ion implantation into the wafer, etching material applied to the wafer, and other similar processes. These processes are used to create the electronic components and connections on the wafer that form a useful electronic circuit.
As these processes are performed on the wafer, the wafer may be subjected to parametric testing. Parametric testing involves testing the electronic parameters of the circuitry on the wafer, such as by applying current or voltage, and by measuring resistance, capacitance, current, voltage, or other such electrical parameters. These tests are used to ensure that a fabricated structure on the semiconductor meets the specifications and requirements of the semiconductor manufacturer and falls within acceptable tolerances.
Parametric testing can take place during the fabrication process to ensure that each stage of fabrication is successful, and is usually performed on the completed wafer to ensure that each completed circuit on the wafer is functional and meets specified performance criteria.
This parametric testing is typically performed with a parametric test system, which comprises several parts. Such systems may be capable of loading a wafer from a wafer tray to a wafer chuck, which is then positioned by a wafer positioner to a proper alignment under a test pin. Once the equipment has properly loaded and moved the wafer into position, parametric test instrumentation systems are initialized and operated to apply electrical signals, heat, and other stimuli as needed to the wafer. The test instrumentation also then takes measurements of parameters, such as impedance and current or voltage measurement, and the test system analyzes and records the results of the parametric tests.
Although parametric testing is typically used to verify the parameters or performance of production semiconductors, such testing can also be critical in investigating the usability or performance characteristics of new materials or new circuit structures. A wide variety of tests, including resistance, capacitance, transistor characteristic, thermal characteristic, and other tests enable characterization of these new materials and circuits, as well as verification of performance in a production environment.
Testing a single wafer can involve tens of thousands of measurements per wafer, with dozens of wafers per manufacturing lot or wafer tray loaded for test. Because this typically results in literally millions of parametric tests and measurements that must be performed per wafer lot, the complexity and speed of the parametric testing system is an important component in the efficient and profitable operation of a semiconductor fabrication facility.
Fabrication facilities desiring to stay efficient and competitive therefore regularly change or upgrade the equipment they use, including probers, wafer loaders, and various measurement instrumentation systems. However, reconfiguration of a semiconductor parametric test system to incorporate new equipment is typically time consuming and expensive, requiring extensive reconfiguration of hardware and software. Highly customized semiconductor parametric test systems have therefore traditionally been prohibitively expensive to produce, given the limited life and upgradeability of such systems.
It is therefore desirable to operate a semiconductor parametric test system that is both configurable and upgradable without extensive redesign of the entire semiconductor parametric test system.